TWO MEN ROBBED TWO WOMEN AT GUNPOINT IN MARINA LAST (SUN) NIGHT.     OFFICIALS SAY THE WOMEN WERE SELLING FLOWERS IN THE PARKING LOT OF FOOD CORRAL MARKET AROUND 10:20 P-M WHEN THE SUSPECTS APPROACHED THEM. ONE OF THE MEN POINTED A GUN AT THEM WHILE THE OTHER TOOK THEIR CASHBOX.    AN OFFICER PURSUED A CAR HE SPOTTED LEAVING THE SCENE.    AFTER STOPPING THE VEHICLE ON SEACREST AVENUE, THE PASSENGER FLED ON FOOT.    THE DRIVER, 21-YEAR-OLD SEAN UNDERWOOD, WAS BOOKED INTO MONTEREY COUNTY JAIL ON SUSPICION OF ROBBERY, VIOLATING PAROLE, VEHICLE PURSUIT, AND GUN CHARGES.